Static sensing orifices and associated pressure transmitters and lines must be protected against the ingress and accumulation of water and moisture in order to ensure, inter alia, disruption-free operation of an air data system, i.e. a data source for flight control and flight guidance. The sensing orifices are usually disposed in the region of an outer skin of an aircraft fuselage. Typically, the sensing orifices are combined with water separators or water traps, which are disposed in the lines in order to separate and collect the water. However, these water separators are expensive to integrate into the aircraft, in inspection, in operation, in maintenance and in repair. In addition, water separators require corresponding maintenance flaps or doors for inspection, operation, maintenance and repair, which however significantly reduce the cloaking and stealth characteristics of the aircraft. Furthermore, their ability to function depends on gravity, which means that they only work properly in normal flight. Inverted flight, and in particular a sustained inverted flight, poses a problem.